Maybe they should be stealthy, at least for some of them? Cultists and such right? If your R'lyeh is Rising people are attending cult meetings and invoking the spirits from beyond, you'd thing they'd do it discreetly...
No, there's always a visiting historian who stumbles into a dark basement and see's something they shouldn't then miraculously escapes. I guess it's hard to be discreet whilst foaming at the mouth.